Syringe being filled from a phial of the Oxford-AstraZeneca vaccine against SARS-CoV-2, the cause of Covid-19. The vaccine contains an adenovirus that normally infects chimpanzees that has been altered so that it has SARS-CoV-2 spike proteins in its outer membrane. The proteins stimulate an immune response, causing the body to produce antibodies against the spike protein. This means that the body is primed to attack the virus should it be encountered after vaccination, preventing disease. The vaccine was approved in the UK on 30th December 2020.